Computer systems, communications systems, and other electronic devices often utilize integrated circuit memories for storing data. For example, dynamic random access memories (DRAMs) provide dense solid-state data storage that is quickly accessed for reading or writing. DRAMs are a volatile form of memory; stored data is lost when power is removed. DRAMs also must typically be refreshed in order to maintain the stored data. In another example, static random access memories (SRAMs) provide volatile data storage that avoids any periodic refresh requirement. "Flash" and other electrically erasable and programmable read-only memories (EEPROMs) provide nonvolatile data storage; stored data is maintained when power is removed. Access and programming times may be longer for EEPROMs than for DRAMs. Other types of commercial memory integrated circuits are also available.
Many applications require large amounts of memory capacity in order to meet data storage requirements. For many such applications, several memory integrated circuits are each individually disposed in an integrated circuit package, and the packages are mounted on a printed circuit board. The printed circuit board is then plugged into an available slot in the computer system or other electronic device such that a microprocessor can access the memory integrated circuits for storing and retrieving data. For applications requiring even larger amounts of memory capacity, several such printed circuit boards carrying memory integrated circuits are plugged into available slots for use by the computer system or other electronic device.
Modem computer systems, communications systems, and other electronic devices demand a high degree of functionality in a minimum volume, for portability and other reasons. Moreover, the electronics industry often uses standardized integrated circuit packages, so that system designers can design and build a computer system using standard components. Because the "footprint" of a standardized integrated circuit package (i.e., its size, connection locations, etc.) is known, the system designer can design the other portions of the computer system assuming a standard integrated circuit package. Thus, a computer system can be designed even before the design of the actual memory integrated circuits carried within the standard integrated circuit package. Such flexibility is particularly important in the computer industry, in which product design cycles are extremely short. Products not timely introduced with the maximum available functionality may not be marketable. Thus, there is a strong need for electronics products that are designed with standardized integrated circuit packages, but which offer maximum functionality while occupying a minimum volume.